Purification and Characterization of Bacillus subtilis Methyl - accepting Chemotaxis Protein Methyltransferase 11

A Bacillus subtilis methyltransferase capable of methylating membrane-bound methyl-accepting chemotaxis proteins (MCPs) of a chemotaxis mutant was purified to homogeneity. MCPs are normally unmethylated in this strain. Results of gel filtration chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicate that the enzyme is a 30,000 molecular weight monomer. The nzyme transfers methyl groups from S-adenosylmethionine to glutamate residues of the substrates. The enzyme is activated by divalent cations and has a K,,, for S-adenosylmethionine of about 5 p ~ . It is competitively inhibited by S-adenosylhomocysteine, with a Ki of about 0.2 PM, and exhibits an in vitro assay pH optimum of 6.9. This methyltransferase i s very different from another methyltransferase from B. subtilis, described previously (Ullah, A. H. J., and Ordal, G . W. (1981) Biochem. J 199, 795-805).